Hard to say without knowing if you intend to stream locally (one machine to another), or from the Internet , or both. I use Netflix w/ a basic wireless G router and it works just fine. But of course, Netflix limits the quality of those streams much more than you would typically do so locally, machine to machine. Wireless N is almost a requirement if you intend to stream uncompressed, 1080p. Streaming can also be affected by other users/devices on the same network. In that case, QoS (Quality of Service) features may prove important.
So before making any purchase decision (including whether your current equipment is up to the task), consider all the ways you use your network, now and in the future.